All I have in the plugin folder is the library.js file (with the console.log statement) and the plugin.json file (with 5 items).

I can download and install external plugins through the dashboard without problems.

I've resolved the issue with the theme being applied - I had been running the app with 'node app.js' which was not allowing the server to restart correctly. Once I started the server with the ./nodebb start command, it could restart correctly and apply the theme / skin.

I've also updated to the 0.7.x build as I need to use the write api, this hasn't resolved the issue.

As of v0.0.5, “installing” a plugin by placing it in the /plugins folder is still supported, but keep in mind that the package id and its folder name must match exactly, or else NodeBB will not be able to load the plugin. This feature may be deprecated in later versions of NodeBB.

Has this been deprecated now? Would this explain why it isn't showing up in the admin console?

So now, I have questions to the NodeBB development team. @julian
About @frissdiegurke 's idea.
What do you think? Is it secure or do you have any better ideas, policies , plans?
To manage dependencies between plugin,
Can we enforce to install and activate plugins by dependencies?
Or can we give warnings of wrong configurations, dependencies and so on by plugin on admin UI ( dash board? )?
Do we have secure way to add/remove/modify custom data by plugin in a filtering pipe?
For example, on filtering hook, data.pluginData.<plugin name> can be always for plugins (means some sure for core will not use it for different reason!! ), whether they are removed or not after filtering. I know if I select good name( random or highly uniq), then it will be quite safe but it will be better if we have an official space.
If I want to make a npm module which is dedicated to NodeBB while it's not a plugin, then what is good name for. Maybe nodebb-helper-any-name. It may be for individual plugins.
I had one more, but I forgot what was it while writing....

Hey there! Thanks for investigating a fix
You can fork the plugin on the GitHub pages, and when you are ready you can submit a pull request to merge those changes back into the upstream repository. Then your work can be shared to everybody!